The present invention relates to a high speed combination electrostatic copying machine and facsimile transceiver.
Copying machines known in the art utilize light, static electricity, heat, magnetism, etc. to directly copy an original document onto a reproduction medium such as a sheet of paper. Such copying machines cannot be readily adapted to bifunction as facsimile transceivers.
Further known in the art is an electrostatic copying machine comprising a linear photosensor array. The individual photosensor elements of the array are strobed in sequence to produce output signals and thereby scan an original document in the horizontal direction. Vertical scan is effected by means of physical movement of the document. The output signals of the photosensor array are fed to a linear array of electrostatic recording electrodes which are energized in accordance with the signals to apply an electrostatic charge pattern to a sheet of copy paper. A toner substance is applied to the paper to develop the electrostatic pattern into a visible image.
This type of copying machine tends to be slow in operation since each horizontal scan line must be scanned and printed before the next line can be scanned. Since the recording electrodes must be energized for a certain length of time to produce an electrostatic charge pattern, the operating speed of such a prior art copying machine cannot be increased beyond a corresponding value without sacrificing resolution.
An expedient which may be employed to increase the copying speed in such a machine is to reduce the number of photosensor elements in the array (and thereby reduce the horizontal scan density) and/or reduce the number of horizontal scan lines per unit vertical distance (and thereby the vertical scan density). However, such reduction of the scan density tends to degrade the copy resolution to a unacceptable extent in actual application. For this reason, it has heretofore been impossible to provide both acceptably high resolution and copying speed in such a copying machine.